Max Planck Institute for the Science of Light

White light sources being several orders of magnitudes brighter than light bulbs, the manipulation of single photons or the smallest focal point in the world – these are just a few skills mastered or developed by the scientists of the Max Planck Institute for the Science of Light. Their main goal is to control light in all dimensions: in time and space, polarisation – i.e. simply speaking the direction of oscillation – and quantum properties. The knowledge they develop could simplify telecommunication or enable more compact data storage. For this purpose the researchers use novel optical structures like optical glass fibres with a regular lattice of tiny hollow channels along its length. Glass fibres guide light with extremely low losses and can be several kilometres long.

Techniques that provide insights into the nanoworld continue to garner Nobel Prizes. However, none of those methods has made it possible to observe exactly how enzymes and other biomolecules function. Frank Vollmer, Leader of a Research Group at the Max Planck Institute for the Science of Light in Erlangen, has now changed all that – with a plasmonic nanosensor.

Soon, the NSA and other secret services may no longer be able to secretly eavesdrop on our communications without being detected – at least if quantum cryptography becomes popular. A team headed by Christoph Marquardt and Gerd Leuchs at the Max Planck Institute for the Science of Light in Erlangen is laying the foundations for the tap-proof distribution of cryptographic keys even via satellite. For the time being, the researchers have brought quantum communication into the light of day.

Light can exert forces that have a significant impact on the nanoscale, enabling control of the mechanical movement of structures smaller than a human hair. This type of physics promises a variety of applications, from highly sensitive measurements to signal transduction in quantum communication. Researchers at the Max Planck Institute for the Science of Light have now predicted how the transport of light and sound can also be controlled in this way. So-called 'topological boundary channels' promise novel signal transmission.

Photonic crystal fibres (PCF) are strands of glass, not much thicker than a human hair, with a lattice of hollow channels running along the fibre. If they are continuously twisted in their production, they resemble a multi-helix. Twisted PCFs show some amazing features, from circular birefringence to conservation of the angular momentum. The biggest surprise, however, is the robust light guidance itself, with no visible fibre core. The basis for this are forces which, like gravitation, are based on the curvature of space.

Nanoscopic solid-state quantum systems are gaining significant momentum in quantum optics. Their ability to integrate into photonic nanostructures makes them promising candidates for the realization of future quantum networks. Efficient coupling of single molecules to photonic waveguide structures was recently demonstrated as an elementary building block. It should be possible to investigate the optical coupling between individual quantum systems by employing novel microresonator architectures. In the meantime, single ions in a crystal also find their application in nano-quantum optics.

By adapting a mode of the light field to a system under study, the interaction of light with matter can be optimized. In this context, the spatial distribution of the electric field of such a tailored mode plays an important role. At the MPI for the Science of Light, this approach is utilized to couple light to individual atoms or nano-particles. It was shown, for example, that light can be coupled to an ion trapped in a parabolic mirror with high efficiency. In other studies, the scattering behavior of individual nano-particles was controlled using polarization tailored light.

Our research is focused on the physics of biosensing, the physical principles for detecting molecules and their interactions. Of particular interest is the study of photonic microsystems with the goal of single molecule analysis. Taking detection to this limit is only possible if the interaction of light with biomolecules is sufficiently enhanced. Our group has now achieved such extreme enhancements with optical microcavities.